Pattern generators, calibration systems and methods for patterning workpieces

ABSTRACT

A pattern generator includes: a writing tool and a calibration system. The writing tool is configured to generate a pattern on a workpiece arranged on a stage. The calibration system is configured to determine a correlation between a coordinate system of the writing tool and a coordinate system of a calibration plate on one of the stage and the workpiece. The calibration system is also configured to determine the correlation at least partly based on an optical correlation signal, or pattern, in a form of at least one optical beam being reflected from at least one reflective pattern on the surface of the calibration plate.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This nonprovisional U.S. patent application claims priority under 35U.S.C. 119(e) to provisional U.S. patent application No. 61/282,584,filed on Mar. 3, 2010, the entire contents of which are incorporatedherein by reference.

The entire contents of U.S. patent application Ser. No. 12/591,954,filed on Dec. 4, 2009 and U.S. provisional patent application No.61/193,522, filed on Dec. 5, 2008, are incorporated herein by reference.

The entire contents of U.S. patent application Ser. No. 11/711,895,filed on Feb. 28, 2007, is also incorporated herein by reference.

BACKGROUND

Pattern matching is useful in performing fast real-time alignment whenpatterning a workpiece. In at least some cases, however, performingsufficiently precise pattern matching and/or determining locations ofpixels in a pattern to be generated on a workpiece with sufficientprecision is somewhat difficult.

SUMMARY

Example embodiments describe a pattern generator comprising acalibration system configured to determine a correlation between acoordinate system of a writing tool and a coordinate system of acalibration plate at least partly based on an optical beam reflectedfrom the calibration plate.

According to at least some example embodiments, the calibration systemis configured to determine a correlation between the coordinate systemof the writing tool and the coordinate system of a calibration plate onone of the workpiece and the stage (e.g., a reference board attached tothe carrier stage) at least partly based on at least one opticalcorrelation signal, or pattern, in the form of at least one optical beamreflected from at least one reflective pattern on the surface of thecalibration plate.

According to at least some other example embodiments, the correlationbetween the coordinate system of the writing tool and the coordinatesystem of the calibration plate is determined at least partly prior tothe generating of the pattern on the workpiece.

According to at least some example embodiments, the calibration systemis configured to determine the correlation while the writing tool isgenerating the pattern on the workpiece and the pattern generator isconfigured to perform real-time alignment of the pattern at least partlybased on an optical beam reflected from the calibration plate, forexample, an optical correlation signal, or pattern, in the form of atleast one optical beam reflected from at least one reflective pattern onthe surface of the calibration plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be described with regard to the drawings inwhich:

FIG. 1 illustrates a simplified example embodiment of a measurementdevice or tool in which a laser beam is reflected along an arm of arotator;

FIG. 2 shows a measurement device including a rotator according to anexample embodiment;

FIG. 3 shows a measurement device according to another exampleembodiment;

FIG. 4 illustrates a scale arrangement according to an exampleembodiment;

FIG. 5 shows a scale arrangement according to another exampleembodiment;

FIG. 6 shows a portion of a measurement device including an overheadscale according to an example embodiment;

FIG. 7 shows a portion of a measurement device according to anotherexample embodiment;

FIG. 8 shows a portion of a measurement device according to yet anotherexample embodiment; and

FIG. 9 shows an example embodiment in which reflection from the bottomsurface of a scale is used.

FIG. 10 illustrates an optical path of an example laser direct imaging(LDI) writer and measurement system according to an example embodiment.

FIG. 11 shows a layout of a calibration plate of a measurement systemaccording to an example embodiment.

FIG. 12A schematically shows an extraction of correction (or deviation)functions f_(x)(a) and f_(y)(a) in respective Cartesian directions x andy, as a function of the rotor angle a, to compensate for errors orimperfections in the optical projection of a spatial light modulator(SLM) image to the substrate that is to be exposed by the LDI writer.

FIG. 12B shows an example global coordinate system illustrating exampledependency between the errors or imperfections and the actual positiony₀ of a pixel on the SLM.

FIG. 13 shows an example embodiment in which a calibration plate ismounted on a stage and where a fan of lines of features are scanned withintermediate translations of the stage, in order to determine theangular orientation of the calibration plate.

FIG. 14A shows an example in which a homogeneously illuminated andlit-up block of pixels in the SLM line image traverses a path over areflective vertical bar, this bar being oriented along the main axis ofthe SLM line image.

FIG. 14B is a graph illustrating an example correlation signal resultingfrom the path traversed in FIG. 14A, with a sharp transition between lowand high reflectance.

FIG. 15A shows an example in which a homogeneously illuminated block ofpixels in the SLM line image traverses a path over a reflectivehorizontal bar, this bar being oriented orthogonally to the line imageof the SLM.

FIG. 15B is a graph illustrating an example correlation signal resultingfrom the path traversed in FIG. 15A, with a flatter transition betweenlow and high reflectance as compared to FIG. 14B.

FIG. 16A shows a more detailed illustration of a reflective slantedbarcode pattern on a substrate of otherwise relatively low reflectance.

FIG. 16B is a graph illustrating an example optical correlation signalindicative of the correlation between the SLM line image and thereflective pattern as a function of the angular position of the rotorarm.

FIG. 17 is a more detailed illustration of a portion of the exampleembodiment of the track shown in FIG. 11.

FIGS. 18A and 18B illustrate example graphs for explaining y-scalecalibration according to an example embodiment.

FIG. 19 is a graph for illustrating how repeated use of single-scanmeasurements of trajectories may be peiformed on a calibration plateconfigured as described above with regard to FIGS. 11 and 17 to provideinformation regarding distortion and deviation over a larger area.

FIGS. 20A and 20B illustrate conventional processing systems having acylinder stage.

FIG. 21 illustrates a portion of a pattern generator having a cylinderstage.

FIG. 22 illustrates a portion of another pattern generator having acylinder stage.

FIGS. 23A-23C shows example roll-to-roll printing systems including oneor more cylinder stages.

FIG. 24 shows a workpiece processing system including a plurality ofcylinder stages.

FIG. 25A shows an example cylindrical stage oriented horizontally.

FIG. 25B shows an example cylindrical stage oriented vertically.

FIG. 26 shows an example apparatus for establishing a coordinate systemon a cylinder stage.

FIGS. 27A and 27B illustrate methods for converting from abstractedstandard coordinates to tool and/or stage coordinates and vice versa.

FIG. 28 shows a more detailed view of an example projection systemincluding a cylindrical stage.

FIG. 29 shows several example vacuum or closed environment processesusing a cylindrical stage.

FIG. 30 illustrates an example platform for processing relatively largeand substantially flat substrates.

FIGS. 31A-31C illustrate different example implementations andorientations of a disc-type writing apparatus.

FIGS. 32A-32C illustrate different example implementations andorientations of a ring-type writing apparatus.

FIG. 33 is a perspective view of an example writing apparatus.

FIG. 34 illustrates another example writing apparatus.

FIG. 35 illustrates yet another example writing apparatus.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings, in which some example embodiments are shown.In the drawings, the thicknesses of layers and regions are exaggeratedfor clarity. Like reference numerals in the drawings denote likeelements.

Detailed illustrative embodiments are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments. Exampleembodiments may be embodied in many alternate forms and should not beconstrued as limited to only the example embodiments set forth herein.

It should be understood, however, that there is no intent to limitexample embodiments to the particular ones disclosed, but on thecontrary example embodiments are to cover all modifications,equivalents, and alternatives falling within the appropriate scope. Likenumbers refer to like elements throughout the description of thefigures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of example embodiments. Asused herein, the term “and/or,” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected,” or “coupled,” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected,” or “directly coupled,” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between,” versus “directly between,” “adjacent,” versus“directly adjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the,”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises,” “comprising,” “includes,” and/or “including,” whenused herein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

According to example embodiments, reading and writing/patterning of asubstrate or workpiece is to be understood in a broad sense. Forexample, reading may include microscopy, inspection, metrology,spectroscopy, interferometry, scatterometry, a combination of one ormore of the aforementioned, etc. Writing/patterning may include exposinga photoresist, annealing by optical heating, ablating, creating anyother change to the surface by an optical beam, etc.

Example of substrates include: flat panel displays, printed circuitboards (PCBs), substrates or workpieces in packaging applications,photovoltaic panels, etc.

Example embodiments provide methods and measurement devices formeasuring a position of a laser beam, where the laser beam is reflectedalong an arm of a rotator towards a calibration scale at a given ordesired peripheral position. As will be described in more detail below,the calibration scale (or grating) is a well-defined and spatiallycalibrated pattern of transparent and reflective areas, which transmitor reflect the laser beam.

According to certain example embodiments, at least one detector systemis configured to detect a reflex or transmission of laser light stemmingfrom a laser source emitting laser light that is impinging on a surfacewhile the laser light is scanning over a scale, grating or a calibrationplate.

The detector system may be used for determining the impinging positionon a workpiece of a laser beam (e.g., a writing or reading beam)emitting light impinging on a workpiece.

In certain example embodiments, the detector system may comprise controlmeans for correcting a deviation from a desired writing or reading beamposition, for example, by adjusting the impinging position on aworkpiece of the writing or reading beam. In a writer system, thewriting beam may be used for ablating a surface or for creating apattern on a workpiece such as a substrate or a wafer.

According to certain example embodiments, correction of the writingbeam, or reading beam, position may be achieved by steering the writingbeam during movement of an optical system, for example, by adjusting theimpinging position of at least one writing beam on a workpiece.

According to at least one other example embodiment, correction of thewriting beam position may be achieved by using an optical component suchas a mirror (e.g., a deformable mirror) for steering the writing beamduring the movement of the optical system.

According to yet another example embodiment, the position of a writingbeam, or a reading beam, may be corrected between the scanning sweeps.

Example embodiments are related to pattern generators, measurementsystems, measurement devices and measurement tools. For the sake ofclarity, example embodiments are discussed with regard to a patterngenerator including a rotator. The rotator may include one or more arms(e.g., 2, 3, 4, 5, 6 or even more arms), and each arm may include anoptical system configured to write/pattern or read a pattern or image.In one example, the reading/writing head of an arm is stationary oressentially stationary and the optical image is translated by a rotatingor swinging optical system from a position near the axis of rotation toa position further away from the axis of rotation. In one example, therotating system may include two parallel mirrors, and may therefore scana circle on the workpiece.

Measurement data (e.g., peripheral position data) determined accordingto example embodiments may be combined with other position measurementdevices (e.g., linear encoders or interferometers) for the y positionand with rotational encoders for the x position. The combination mayprovide more absolute Cartesian coordinates during full revolutions andover full linear motion of a system.

Example embodiments may be utilized in conjunction with a continuouslyrotating system, which exchanges relatively little or no energy andrelatively small vibrations with the environment.

At least one example embodiment provides a measurement device formeasuring a peripheral position in a Cartesian coordinate system.According to at least this example embodiment, the measurement deviceincludes: a rotating laser source, a reflector, a scale and a detector.The rotating laser source is configured to emit a rotating laser beamalong a radius of a rotator. The reflector is configured to reflect thelaser beam in a direction orthogonal to a path of the laser beam. Thescale has a pattern of transparent and reflective areas, and ispositioned at a peripheral position of the measurement device. Thedetector is configured to provide a sequence of pulses by detecting areflex or transmission of the rotating laser beam while the laser beamscans over the scale. The sequence of pulses corresponds to Cartesiancoordinates of the system.

At least one other example embodiment provides a method for measuring aperipheral position in a Cartesian coordinate system. According to atleast this example embodiment, a rotating laser beam is emitted along aradius of a rotator; the rotating laser beam is reflected in a directionorthogonal to a path of the laser beam; and a sequence of pulses isprovided by detecting a reflex or transmission of the rotating laserbeam while the laser beam scans over a pattern of transparent andreflective areas positioned at a peripheral area of the measurementdevice. The sequence of pulses corresponds to Cartesian coordinates ofthe system.

According to at least some example embodiments, the rotator includes aplurality of arms, and the reflector is configured to reflect the laserbeam along one of the plurality of arms of the rotator. Every otherpulse in the sequence of pulses represents a position in a firstdirection of the Cartesian coordinate system. A time difference betweenconsecutive pulses represents a position in a second direction of theCartesian coordinate system.

According to at least some example embodiments, the detector may bearranged on an upper portion of the scale.

According to at least some example embodiments, the measurement devicemay further include a bearing (e.g., an air bearing pad) configured tomaintain a fixed relative distance between the scale and the table.According to at least some example embodiments, at least one air bearingis configured to maintain a fixed relative distance (or position)between the scale and the table orthogonal to the direction of movementof the table by providing the at least one air bearing between the tableand a support member of the scale.

According to at least some example embodiments, the measurement devicemay further include a spring loaded pad and a bearing configured toguide the scale along a side of the table.

According to at least some other example embodiments, the measurementdevice may include at least one pad (e.g., an air bearing pad) formaintaining a relative position between the scale and the table byextending the guiding along the side of the table in the movingdirection of the table (y direction) so that the scale follows the tablerotation.

According to at least some other example embodiments, the measurementdevice may include at least two spring loaded pads configured tomaintain the scale at a fixed position over the table by sliding alongthe side of the table at a given or defined distance.

According to at least some other example embodiments, the measurementdevice may include at least one spring loaded pad (e.g., air bearingpad) for maintaining a distance between the support member of the scaleand the table in a direction orthogonal to the moving direction of thetable and at least one second pad (e.g., air bearing pad) extending theguiding along the side of the table in the moving direction of the table(y direction) so that the scale follows the table rotation.

The laser source may be separate from a source configured to emit anexposure beam. In this case, the reflector may be configured to reflectthe laser beam in a first direction toward the scale and to reflect theexposure beam in a second direction toward the workpiece. Alternatively,the reflector may be configured to reflect the laser beam and theexposure beam in the same direction. In this case, the laser beamemitted by the laser source may also serve as an exposure beam forexposing a workpiece. The reflector may reflect a first portion of thelaser beam toward the workpiece for exposing the workpiece and a secondportion of the laser beam toward the scale. Alternatively, the firstportion of the laser beam and the second portion of the laser beam maybe reflected in opposite directions.

According to at least some example embodiments, the laser beam may bereflected toward the workpiece for exposing the workpiece, and areflected portion of the laser beam for exposing the workpiece may bereflected back toward the scale, which is arranged above the reflector.

FIG. 1 illustrates a simplified, example embodiment of a measurementdevice or tool in which a laser beam is reflected along an arm (orradius) of a rotator.

Referring to FIG. 1, a laser beam 108 scans over a scale or grating 110in the clockwise (or θ) direction. A reflex and/or transmission of thelaser beam 108 is detected by a detector (not shown). The detectorgenerates a detector signal D_S composed of a sequence of pulses 106based on the detected reflexes and/or transmissions of the laser beam108. The detector may generate a pulse for each detected reflex and/ortransmission of the laser beam 108, and the sequence of pulsescorresponds to Cartesian coordinate(s).

According to at least this example embodiment, the detector may be anydetector configured to generate a sequence of pulses based on detectedreflexes or transmissions of light. In one example, the detectordiscussed above with regard to FIG. 1 may be any standard orconventional light detector that measures the intensity of light.

Still referring to FIG. 1, the scale 110 includes vertical slits 102 andslanted slits 104. In this example, every other pulse 106-n of thedetector signal D_S corresponds to a specific x position in theCartesian coordinate system, and the time Δt between two consecutivepulses corresponds to a specific y position in the Cartesian coordinatesystem.

FIG. 2 shows a measurement device or system including a rotatoraccording to an example embodiment.

Referring to FIG. 2, the measurement device includes a rotator 208having four arms 202. The rotator 208 is arranged above a base 210. Atable 212 is arranged on the base 210 and capable of holding a workpiece214.

In example operation, a laser source 206 emits a rotating or scanninglaser beam 200 toward the rotator 208. The laser beam 200 is reflected(e.g., by a reflector, which is not shown) along an arm 202 of therotator 208 toward a scale 204 arranged at the periphery of the table212.

Still referring to FIG. 2, another reflector (also not shown in FIG. 2)reflects the laser beam 200 upward towards the scale 204. As the laserbeam 200 scans across the scale 204, the scale 204 reflects the laserbeam 200 back toward a detector located at a non-rotating position. Inat least this example embodiment, the detector may be located near thelaser source in a non-rotating location, and the returning light may bereflected horizontally (e.g., 90 degrees from the vertical beam in FIG.2) by a 45 degree semi-transparent plate (not shown).

As the laser beam 200 scans the scale 204 in FIG. 2, the detectorgenerates a detector signal including a sequence of pulses. As discussedabove with regard to FIG. 1, for example, every other pulse of thedetector signal corresponds to a specific x position in the Cartesiancoordinate system, and the time Δt between two consecutive pulsescorresponds to a specific y position in the Cartesian coordinate system.Thus, Cartesian coordinates of a given or desired peripheral positionmay be determined based on the generated detector signal.

As was the case with FIG. 1, the detector discussed above with regard toFIG. 2 may be any standard or conventional light detector that measuresthe intensity of light.

According to at least some example embodiments, the scale 204 and/or thetable 212 may be configured to move in the x and/or y directions suchthat the scale 204 is positionable relative to the table 212.

FIG. 3 shows a measurement device according to another exampleembodiment. The measurement device shown in FIG. 3 is similar to themeasurement device shown in FIG. 2, except that the transmission oflight is measured on the backside of the scale. In FIGS. 2 and 3, likenumerals refer to like elements.

Referring to FIG. 3, the measurement device includes the rotator 208having four arms 202. The rotator 208 is arranged above the base 210.The laser source 206 emits a rotating laser beam 300 toward the rotator208. The rotating laser beam 300 is reflected along one of the arms 202by a reflector (not shown). The laser beam 300 is then reflected uptowards the scale 304 at the periphery of the table 212 by anotherreflector (also not shown). As the laser beam 300 scans across the scale304, the laser beam 300 is transmitted through the scale 304 anddetected by a detector 306 arranged on or relatively close to an uppersurface (e.g., backside) of the scale 304.

In this example embodiment, the detector 306 generates a detector signalincluding a sequence of pulses. As discussed above with regard to FIGS.1 and 2, for example, every other pulse of the detector signalcorresponds to a specific x position in the Cartesian coordinate system,and the time Δt between two consecutive pulses corresponds to a specificy position in the Cartesian coordinate system. Thus, Cartesiancoordinates of a given or desired peripheral position may be determinedbased on the generated detector signal.

As was the case with FIGS. 1 and 2, the detector 306 discussed abovewith regard to FIG. 3 may be any standard or conventional light detectorthat measures the intensity of light.

In a system with a combination of rotational and prismatic movement(where the prismatic movement is, e.g., a moving table), the relativeposition in the direction orthogonal to the movement may be measured byguiding the scale 204, 304 along the side of the table 212 with abearing. To handle rotation of the table 212, two or more guiding padsmay be added such that the scale 204, 304 follows the rotation of thetable 212.

According to example embodiments, the spring loaded guiding pads may beimplemented in a number of ways. For example, the spring loaded guidingpads may be air bearings, sleeve bearings, magnetic bearings, etc. Thepads are capable of sliding along the side of the table at a given ordefined distance in the orthogonal direction, and thereby maintain thescale at a fixed position over the table.

FIG. 4 illustrates a portion of a measurement device according to anexample embodiment. In this example embodiment, the scale 404 isattached to a spring loaded pad 406 guided with a bearing along the sideof the table 212.

FIG. 5 shows a portion of a measurement device configured similar to theportion of the system shown in FIG. 4, but with two more pads 502 and504 added to adjust the scale rotation according to the table rotation.In FIG. 5, the two extra pads 502 and 504 extend the guiding along theside of the table 212 in the y direction so that the scale 404 followsthe table rotation.

FIGS. 6 through 9 illustrate portions of measurement devices configuredto reflect a measuring beam toward/on a scale according to differentexample embodiments. As shown and described in more detail below, themeasuring beam may be derived from an exposure beam or from a completelyseparate laser source.

FIG. 6 shows a portion of a measurement device including an overheadscale according to an example embodiment. In this example embodiment,the measuring laser beam 606 is derived from a laser source 608, whichis separate from the source of an exposure beam 614.

Referring to FIG. 6, in example operation, a laser source 608 emits arotating laser beam 606 toward an arm 602 of a rotator. The laser beam606 is directed along the arm 602 toward a reflector 610. The reflector610 reflects the laser beam 606 toward the scale 604, which is arrangedabove the table 612. The laser beam 606 scans across the scale 604, andtransmissions or reflexes of the laser beam 606 are detected by adetector (not shown).

In this example, the detector may generate a detector signal based onthe detected transmissions or reflexes of the scanning laser beam 606,and the Cartesian coordinates of a given or desired peripheral positionmay be determined based on the sequence of pulses comprising thedetector signal. The detector discussed above with regard to FIG. 6 maybe any standard or conventional light detector that measures theintensity of light.

According to at least the example embodiment shown in FIG. 6, thereflector 610 is arranged between the table 612 and the scale 604.

FIG. 7 shows a portion of a measurement device including a scaleaccording to an example embodiment. In this example, the scale isarranged closer to the surface of a stage as compared to the exampleembodiment shown in FIG. 6. The measuring laser beam 706 in FIG. 7 isderived from a laser source 708, which is separate from the source of anexposure beam 714.

Referring to FIG. 7, the laser source 708 emits the rotating laser beam706 toward an arm 702 of a rotator. A reflector (not shown) directs thelaser beam 706 along the arm 702 toward another reflector 710. Thereflector 710 reflects the laser beam 706 downward toward the scale 704,which is arranged above the table 712. As the laser beam 706 scansacross the scale 704, transmissions or reflexes of the laser beam 706are detected by a detector (not shown) as described above.

As discussed above with regard to FIG. 6, the detector may generate adetector signal based on the detected transmissions or reflexes of thescanning laser beam 706, and the Cartesian coordinates of a given ordesired peripheral position may be determined based on the sequence ofpulses comprising the detector signal. The detector discussed above withregard to FIG. 7 may be any standard or conventional light detector thatmeasures the intensity of light.

In this example embodiment, the scale 704 is arranged between thereflector 710 and the table 712.

According to at least some example embodiments, light used to expose aworkpiece may be used to scan the scale.

FIG. 8 shows an example embodiment in which a portion of an exposurebeam for exposing a workpiece is used to scan a scale and determineCartesian coordinates of a peripheral position. In this exampleembodiment, the measuring laser beam 806 is derived from the exposurebeam.

Referring to FIG. 8, in example operation, a laser 808 emits therotating laser beam 806 toward an arm 802 of a rotator. A reflector (notshown) reflects the laser beam 806 along the arm 802 toward anotherreflector 810. The reflector 810 reflects a portion of the laser beam806 toward the table 812 and another portion of the laser beam 806downward toward the scale 804, which is arranged above the table 812. Asthe laser beam 806 scans across the scale 804, reflexes of the laserbeam 806 from an upper surface of the scale 804 are detected by adetector (not shown) as described above.

As discussed above, the detector may generate a detector signal based onthe detected transmissions or reflexes of the scanning laser beam 806,and the Cartesian coordinates of a given or desired peripheral positionmay be determined based on the sequence of pulses comprising thedetector signal. The detector discussed above with regard to FIG. 8 maybe any standard or conventional light detector that measures theintensity of light.

FIG. 9 shows an example in which reflection/transmission from the bottomsurface of a scale is used to determine Cartesian coordinates of aperipheral position. In this example embodiment, the measuring laserbeam 906 is derived from an exposure beam.

Referring to FIG. 9, a laser 908 emits the rotating laser beam 906toward an arm 902 of a rotator. A reflector (not shown) directs thelaser beam 906 along the arm 902 of the rotator toward areflector/deflector/optical element 910. The reflector/deflector 910directs the laser beam 906 upward toward the scale 904. As the laserbeam 906 scans across the scale 904, the laser beam 906 is reflectedback toward the optical element 910 by the scale 904. The reflectedlaser beam 906 passes back through the optical element 910 and impingesthe table 912 and/or is detected by a detector (not shown). As discussedabove, the detector may generate a detector signal based on the detectedtransmissions or reflexes of the scanning laser beam 906 and theCartesian coordinates of a given or desired peripheral position may bedetermined based on the sequence of pulses comprising the detectorsignal. The detector discussed above with regard to FIG. 9 may be anystandard or conventional light detector that measures the intensity oflight.

Example embodiments also provide pattern generators in which a relationor correlation between the coordinate system(s) of a calibration plateand/or board and the writer system is utilized during patterning. Thisrelation or correlation may be provided by a calibration system beforepatterning and may be utilized for relatively fast real-time alignmentduring patterning of the workpiece.

Example embodiments are discussed in some instances with regard to arotating system. However, example embodiments are not limited thereto.Rather, example embodiments are applicable to different stage conceptsand printing technologies such as cylinder stages, helix concepts forroll-to-roll printing, etc. Furthermore, example embodiments are not belimited to using a diffracted portion of a writing beam impinging on apattern on a calibration plate and/or board. Rather, in alternativeembodiments, a separate beam or SLM aerial image impinging on thepattern of the calibration plate and/or board may also be used forrelatively fast real-time alignment during patterning.

According to at least some example embodiments, the calibration systemis configured to determine a correlation between a coordinate system ofthe writing tool and a coordinate system of a calibration plate at leastpartly based on an optical beam reflected from the calibration plate.

According to at least some example embodiments, the calibration systemis configured to determine a correlation between the coordinate systemof the writing tool and the coordinate system of a calibration plate onone of the workpiece and the stage (e.g., a reference board attached tothe carrier stage) at least partly based on at least one opticalcorrelation signal, or pattern, in the form of at least one optical beamreflected from at least one reflective pattern on the surface of thecalibration plate.

According to at least some example embodiments, the calibration plate isa reference board having a fixed relation to the carrier stage on whichthe workpiece is placed. In one example, the reference board may beattached to the carrier stage.

According to at least some example embodiments, the calibration systemis configured to determine a correlation between the coordinate systemof the writing tool and the coordinate system of a calibration plate onone of the stage and the workpiece, at least partly based on aone-dimensional pattern, or image, reflected from the calibration plate.

According to at least some other example embodiments, the calibrationsystem is configured to determine a correlation between the coordinatesystem of the writing tool and the coordinate system of a calibrationplate on one of the stage and the workpiece, at least partly based on atwo-dimensional image, or pattern, reflected from the calibration plate.

According to at least some example embodiments, the calibration systemis configured to determine a correlation between the coordinate systemof the writing tool and the coordinate system of a calibration plate onone of the stage and the workpiece, while generating the pattern on theworkpiece. The calibration system may be configured to determine thecorrelation between the coordinate system of the writing tool and thecoordinate system of the calibration plate while simultaneously, orconcurrently, generating the pattern on the workpiece.

According to at least some example embodiments, the pattern generator isconfigured to perform real-time alignment of the pattern based on thedetermined correlation between the coordinate system of the writing tooland the coordinate system of the calibration plate.

According to at least some example embodiments, the calibration systemis configured to determine the correlation while the writing tool isgenerating the pattern on the workpiece and the pattern generator isconfigured to perform real-time alignment of the pattern at least partlybased on an optical beam reflected from the calibration plate, forexample, an optical correlation signal, or pattern, in the form of atleast one optical beam reflected from at least one reflective pattern onthe surface of the calibration plate.

According to at least some example embodiments, the correlation betweenthe coordinate system of the writing tool and the coordinate system ofthe calibration plate is determined at least partly during thegenerating of the pattern on the workpiece.

According to at least some other example embodiments, the correlationbetween the coordinate system of the writing tool and the coordinatesystem of the calibration plate is determined at least partly in betweenthe writing strokes of at least one writing unit of the writing toolgenerating the pattern on the workpiece. In example embodiments, thecorrelation is determined at least partly in between the writing sweepsof one rotor arm of the writer tool and/or in between the writing sweepsof at least two separate rotor arms of the writer tool.

According to at least some other example embodiments, the correlationbetween the coordinate system of the writing tool and the coordinatesystem of the calibration plate is determined at least partly prior tothe generating of the pattern on the workpiece.

According to at least some example embodiments, the calibration systemcomprises or is coupled to a measurement system including means foremitting at least one optical beam toward the calibration plate andrecognition software designed to recognize an optical correlationsignal, or pattern, in the form of the emitted at least one optical beambeing reflected from at least one reflective pattern on the surface ofthe calibration plate.

According to at least some example embodiments, a tailored SLM patternthat interacts with a pattern is introduced to provide a relativelyprecise position of the SLM of the writer system. The relatively preciseposition of the SLM is obtained through a correlation measurement andsubsequently measured (Cartesian) coordinates of the calibration plateand/or board.

FIG. 10 illustrates an optical path of a laser direct imaging (LDI)writer and measurement system 1000 according to an example embodiment.In this example embodiment, an optical beam reflected from a calibrationplate 1100 is collected and sampled by an optical detector 1007. Acalibration system 1016 may then provide information regarding patternorientation, translation and/or scaling based on the collected andsampled optical beam.

The optical beam used for calibration (hereinafter the “opticalcorrelation beam”) is transmitted along a path similar or substantiallysimilar to the path of the optical beam used for writing (hereinafterthe “writing optical beam”), except that the calibration optical beam issampled by the optical detector 1007 as discussed in more detail later.

Referring to FIG. 10, a mirror 1001 reflects the writing optical beam(e.g., a laser beam or beams) emitted from an optical beam source (e.g.,a laser source, which is not shown) toward a spatial light modulator(SLM) 1002. The SLM 1002 reflects the writing optical beam with aspatially modulated image (SLM image) back toward the mirror 1001. Themirror 1001 directs the writing optical beam toward an angled mirror1003. The angled mirror 1003 directs the writing optical beam towarddemagnification relay optics 1010, which demagnify the writing opticalbeam

A semi-transparent astigmator 1008 shapes the demagnified writingoptical beam to a line focus of the LDI writer 1000. Thesemi-transparent astigmator 1008 passes the shaped optical writing beamto a trombone 1006.

The trombone 1006 includes at least two mechanically translatableright-angled mirrors and is configured to change the optical path andhence also the final focus of the writing optical beam.

Referring still to FIG. 10, the trombone 1006 directs the shaped writingoptical beam toward a focus relay 1004. The writing optical signalpasses through the focus relay 1004 to an aerial image 1011 of the SLM,this image positioned just above a reflective pyramid-shaped rotatingprism 1014.

The reflective pyramid-shaped rotating prism 1014 is mechanically lockedto one or more rotor arms. For the sake of clarity, only one rotor arm1020 is shown in FIG. 10. The rotor arm 1020 includes rotor relay optics1012.

The rotor relay optics 1012 focus and direct the writing optical beamtoward the calibration plate 1100. The calibration plate 1100 may bepart of (e.g., integral) or fixed to a stage (not shown) or part of aworkpiece on the stage. As discussed in more detail below, thecalibration plate 1100 includes a plurality of reflective patterns ofareas configured to reflect the writing optical beam for calibrating thespatial position, focus and/or dose of the writing optical beam. Theareas may have different (e.g., relatively high and relatively low)reflectance.

Referring back to FIG. 10, the calibration plate 1100 reflects thewriting optical beam back toward the rotor arm 1020 as the opticalcorrelation beam, resulting from the correlation between the pattern ofthe impinging optical beam and the reflective pattern on the calibrationplate. The optical correlation beam propagates backwards through the LDIwriter 1000 via a path similar or substantially similar (but reverse) tothe optical path of the writing optical beam until reaching thesemi-transparent astigmator 1008.

The semi-transparent astigmator 1008 directs/reflects the opticalcorrelation beam toward an optical detector 1007 and calibration system1016.

The optical detector 1007 generates an analog electrical signal based onthe optical correlation beam. The electrical signal is sampled,analog-to-digitally converted and further analyzed by the calibrationsystem 1016 using algorithms specific to the calibration of the LDIwriter 1000. The calibration system 1016 may be implemented by one ormore central processing units (CPUs), digital signal processors (DSPs),application-specific-integrated-circuits (ASICs), field programmablegate arrays (FPGAs), computers or the like.

In more detail, according to at least some example embodiments, thecalibration system 1016 is configured to measure a step response ofsamples reflected for each rotor arm 1020 and provide a focus map asfunction of rotor angle x(a).

The calibration system 1016 may also be configured to measure opticalintensity in the plane of the calibration plate 1100 and to calibratethe dose controller (not shown) for each rotor arm 1020 and for a set ofpositions along an exposure sweep.

According to at least some example embodiments, the calibration system1016 is configured to measure an orientation of the calibration plate1100, x-offsets and y-offsets of the calibration plate 1100, x-scalesand y-scales of the calibration plate 1100, and a shape and position ofthe SLM image on the calibration plate 1100 as a function of the rotorangle x(a) (e.g., for each rotor arm). Based on these measurements, thecalibration system 1016 may provide a correlation between the coordinatesystems of the calibration plate 1100 and the LDI writer 1000.

In the case of a rotary system, the calibration system 1016 may also beconfigured to measure rotor arm radius, rotor rotation center, and onesingle sweep per rotor arm. Based on these measurements, the calibrationsystem 1016 may provide a relatively fast check of the validity of thecalibration before printing.

In addition, the calibration system 1016 may be configured to measurethe registration of a known pattern over a dedicated glass plate andprovide an extended y-scale as well as compensation for snaking of thestage in orientation or x-direction as the stage moves.

FIG. 11 shows an example embodiment of the calibration plate 1100 inmore detail.

The calibration plate 1100 shown in FIG. 11 is configured to reflect theoptical writing beam for calibrating: spatial position, focus and/ordose of the optical writing beam. According to example embodiments, thecalibration plate 1100 may have areas of different (e.g., relativelyhigh and relatively low) reflectance. In one example, the calibrationplate 1100 may be a chrome or similarly reflective plate.

Referring in more detail to FIG. 11, the calibration plate 1100 includesa plurality of horizontal barcode patterns 1102. Each of the horizontalbarcode patterns 1102 includes a plurality of horizontal bars 1102Harranged in a barcode pattern. The plurality of horizontal barcodepatterns 1102 are configured to produce optical correlation signals formeasuring y-scale and y-offset of the position of the writing opticalbeam.

The calibration plate 1100 further includes a track 1104. The track 1104includes a plurality of sets of vertical bars (x-bars) and a pluralityof slanted barcode patterns. As discussed in more detail below withregard to FIG. 17, the plurality of slanted barcode patterns areinterwoven and/or interlaced between the sets of vertical bars and theslanted barcode patterns are configured to extract actual x andy-positions of a projected SLM line image in a single sweep over thecalibration plate 1100.

Still referring to FIG. 11, the calibration plate 1100 further includesa plurality of pads 1106 for topographic measurement of focus over theextent of the calibration plate 1100. The calibration plate 1100 alsoincludes a relatively sparse raster of other vertical bars 1108 forrelatively coarse calibration of focus.

A plurality of verification pads 1110 are provided to verify modulatordelay compensation and/or timing of, for example, an LDI writer in whichthe calibration plate 1100 may be implemented.

A plurality of fans of lines 1112 are provided for calibrating theangular orientation of the calibration plate 1100. The plurality of fanlines 1112 will be described in more detail later with regard to FIG.13.

An area of dots 1114 are configured for calibrating alignment cameras(not shown) to the coordinate system of the calibration plate 1100.

Still referring to FIG. 11, the calibration plate 1100 further includesa plurality of alignment pads 1116. The plurality of alignment pads 1116are configured for assisting with mechanical alignment of thecalibration plate 1100 during mounting on the stage (not shown).

FIG. 17 is a more detailed illustration of a portion of the track 1104shown in FIG. 11.

As discussed above with regard to FIG. 11, the track 1104 includes aplurality of sets of vertical bars (x-bars) and a plurality of slantedbarcode patterns interlaced (or interwoven) between the plurality ofsets of vertical bars. Although discussed with regard to a plurality ofslanted barcode patterns, the track 1104 may include one or more slantedbarcode patterns. Moreover, according to at least some exampleembodiments, the slanted barcode patterns are oriented obliquelyrelative to the vertical and horizontal bars described herein.

Each of the slanted barcode patterns includes a plurality of slantedbars arranged in a barcode pattern, such as a Barker-code pattern, aBarker-code like pattern or a similar pattern.

Referring to FIG. 17, the slanted barcode pattern 1704 (also referred toas a y-pattern barcode) is positioned between sets of vertical bars1702. Each set of vertical bars 1702 includes a plurality of verticalbars 1702V. The slanted barcode pattern 1704 includes a plurality ofslanted bars 1704S.

The pattern of interweaving the slanted barcode patterns 1704 betweenthe sets of vertical bars 1702 may be repeated (e.g., periodically)throughout the track 1104.

In example operation, by passing a SLM line image along the path of thetrack 1104, the transition between different (e.g., low and high)reflectance of the vertical bars 1702V provides an optical correlationsignal indicative of the x-scale and the x-offset of the calibrationplate 1100. This is described in more detail below with regard to FIGS.14A and 14B.

In the example shown in FIG. 17, the x-coordinates of each vertical bar1702V are known from the design of the calibration plate 1100. Thus, thex-coordinates of the slanted barcode pattern 1704 are obtained byinterpolating over the gap between the sets of vertical bars 1702.

In one example, the position of the correlation peak relative to itsclosest neighboring vertical bar 1702V provides the y-position of thewriting optical beam. This provides the x and y coordinates of where theSLM line image crosses the slanted barcode pattern 1704.

Measuring a full arc of the trajectory pattern provides a complete orsubstantially complete position of the SLM in a total of, for example,152 points. Eight different regions along the SLM are measured, androtor radius R, rotor rotation center (x₀ and y₀), SLM averagex-position as a function of rotor angle x(a), and SLM shape and positiondeviation from an ideal circle defined by the extracted radius androtation center d_(x)n and d_(y)n are extracted. The SLM averagex-position as a function of rotor angle Ma) is used to calibrate anx-order table.

FIG. 16A shows a more detailed illustration of a slanted barcode patternof relatively high reflective bars on an otherwise relatively lowreflective substrate.

FIG. 16B is a graph illustrating an example correlation signalindicative of the correlation between the SLM line image and thereflective pattern depending on the position of the rotor arm.

Referring to FIG. 16A, in this example embodiment, the slanted bars inthe slanted barcode pattern 1606 are arranged in a Barker-code pattern.A SLM line pattern 1604 matching the Barker-code pattern is imaged tothe plane of the calibration plate 1100 as shown in FIG. 16A. As the SLMline image 1604 traverses a path (e.g., an arc path) intersecting theslanted barcode pattern 1606, the reflected optical beam is indicativeof the correlation between the SLM line image 1604 and the slantedbarcode pattern 1606.

As shown in FIG. 16B, the single peak 1602 of the optical correlationsignal corresponds to the position where the SLM line image 1604 matchesthe slanted barcode pattern 1606. A position for the y-coordinate atwhich the SLM line image matches the slanted barcode pattern 1606 isobtained by comparing the position of the correlation peak with thepositions of the nearest neighboring vertical bar.

FIG. 12A schematically shows example correction (or deviation) functionsf_(x)(a) and f_(y)(a). The correction functions f_(x)(a) and f_(y)(a)are used to compensate for errors or imperfections in the opticalprojection of the SLM line image to the substrate that is to be exposedby, for example, an LDI writer (e.g., LDI writer 1000 shown in FIG. 10).

FIG. 12B shows an example global coordinate system illustrating exampledependency between the errors or imperfections and the actual positiony₀ of the pixel on the SLM.

Referring to FIGS. 12A and 12B, after sampling x and y coordinates ofvertical bars and slanted barcode patterns as a function of the rotorangle a along the track 1104 shown in FIG. 11, the obtained set ofcoordinates (x(a), y(a)) are compared to an ideal (or perfect) circular(or elliptical) arc obtained using a least-square regression to theobtained points. The deviations in the coordinates (x(a), y(a)) from theideal circular arc are subsequently extracted as the deviation functionsf_(x)(a) in the x-direction and f_(y)(a) in the y-direction. Whenmapping an SLM pattern to be written on a substrate, the extracteddeviation functions f_(x)(a) and f_(y)(a) may be tabulated andcompensated for in spatial position.

The deviations described by the deviation functions f_(x)(a) andf_(y)(a) also depend on the actual position y₀ of the pixel on the SLMas shown in FIG. 12B.

As shown in FIG. 12B, a pixel 1204 in the aerial image 1011 of the SLMabove the reflective pyramid-shaped prism 1012 shown in FIG. 10, forexample, is reflected through the rotor arm 1020 and toward an image1208 of the SLM pixel on the stage plane (e.g., calibration plate orsubstrate). Depending on the actual position y₀ of the pixel on the SLM,the path traversed by the pixel will be described by the function(x(a,y₀), y(a,y₀)) with the associated deviation functions f_(x)(a, y₀)and f_(y)(a,y₀) mapping the deviation of the trajectory as function ofrotor angle a and position in the SLM 1002.

Still referring to FIGS. 12A and 12B, because the SLM virtual imageposition (0,y₀) just above the reflective pyramid-shaped prism 1012 inthe global coordinate system is known, the fundamental movement isdescribed by Equation (1) shown below.x′=R sin(α)+f _(x)(y ₀,α)y′=−y ₀ +R cos(α)+S _(y) +f _(y),(y ₀,α)  (1)

In Equation (1), the deviation functions f_(x)(a, y₀) and f_(y)(a,y₀)describe the unpredictable portion of the SLM image trajectory, whichneeds to be calibrated. As the pyramid-shaped prism 1012 and theconnected rotor arm 1020 rotates, the trajectory described by Equation(1) provides the motion of an arbitrary pixel at position y₀ of theone-dimensional array of pixels in the SLM. The nominal path for aperfectly aligned and substantially error-free system may be describedby Equation (1) with deviation functions f_(x)(a, y₀) and f_(y)(a, y₀)being zero or substantially zero. However, due to projection errors andoptical aberrations, the path described by the pixels in any real systemno longer follows the ideal circular arc. Rather, the path described bythe pixels follows a path on which the additional deviations describedby f_(x)(a,y₀) and f_(y)(a,y₀) are superimposed in the x and ydirections, respectively. The goal of the calibration is to determinethese deviations together with the effective radius R and offset S_(y)in Equation (1).

After determining these parameters, for example, by measuring thetraversed trajectories on a relatively well-defined and traceablecalibration pattern, the parameters may be applied to compensate forprojection errors and optical aberrations. The determined parametersenable effective error compensation, thereby improving writingperformance.

FIG. 13 shows an example embodiment in which a calibration plate ismounted on a stage.

Referring to FIG. 13, the calibration plate 1302 includes a fan ofreflective bars 1300. In this example, the stage 1304 is travelinglinearly along the y-axis. The fan pattern 1300 shown in FIG. 13corresponds to the fan pattern 1112 described above with regard to FIG.11.

As the path described by the SLM line image intersects the fan pattern1300, a set of correlation peaks in the resulting correlation signal arerecorded as function of the rotor angle a. The correlation peaks aresimilar to those discussed above with regard to FIG. 16B.

As the correlation peaks are repeatedly recorded for different positionsof the stage 1304, the recorded correlation peaks diverge or convergetoward a common line 1306 on the calibration plate 1302. The position ofthis common line 1306 relative to the fan pattern 1300 provides thenecessary information regarding the angular orientation φ₀ of thecalibration plate 1302 relative to the y-axis. The angular orientationφ₀ is used to extract, for example, the x-scale of the calibration plate1302.

According to at least some example embodiments, the calibration system1016 described above with regard to FIG. 10 may provide scaling factorsfor subsequently measured Cartesian coordinates of a calibration platerelative to the writer (axis-of-motion) system.

FIG. 14A shows an example in which a homogeneously illuminated block ofpixels in the SLM line image traverses a path over a reflective verticalbar 1402. FIG. 14B is a graph illustrating an example correlation signalresulting from the path traversed in FIG. 14A.

In more detail, FIG. 14A shows an illuminated block of pixels 1406 in anSLM line image 1404 traversing a path over a reflective vertical bar1402. The reflective vertical bar 1402 is oriented along the y-axis.

As the SLM line image 1404 enters or exits the reflective area of thevertical bar 1402, a steep transition between relatively low andrelatively high reflectance provides a relatively sharp transition inthe optical correlation signal shown in FIG. 14B. The relatively sharptransition in the optical correlation signal shown in FIG. 14B providesa relatively high definition of the position of the vertical bar 1402along the x-axis.

FIG. 15A shows an example in which a homogeneously illuminated block ofpixels in the SLM line image traverses a path over a reflectivehorizontal bar 1502. FIG. 15B is a graph illustrating an examplecorrelation signal resulting from the path traversed in FIG. 15A.

In more detail, FIG. 15A shows a homogeneously illuminated block ofpixels 1506 in an SLM line image 1504 traversing a path over areflective horizontal bar 1502. The reflective horizontal bar 1502 isoriented horizontally along the x-axis.

As shown in FIG. 15B, the transition between relatively low andrelatively high reflectance is no longer relatively sharp as the SLMline image 1504 enters or exits the reflective area of the horizontalbar 1502. Rather, the correlation signal shown in FIG. 15B has slopededges leading to the maximum amplitude of the correlation signal.

In the case of a finite-contrast SLM, with some background light presentin the un-illuminated areas surrounding the illuminated section, thebackground level in the resulting signal may be considerable. Thus,illumination of a relatively large section of the SLM may be required.However, this may result in an even lower slope in the transition (lesssharp transition) in the optical correlation signal. The decrease insharpness results in relatively low precision when determining they-position of the reflective bar. By using barcode patterns (e.g.,Barker or Barker-like coding schemes), this problem may be avoided.

FIGS. 18A and 18B illustrate example graphs for explaining y-scalecalibration according to an example embodiment.

In more detail, FIG. 18A illustrates an example for addressingrelatively low precision in determining the y-position for afinite-contrast SLM image.

As shown in FIG. 18A, rather than illuminating a homogeneous block ofpixels of the SLM as in FIG. 15A, a pattern of illuminated pixels 1800in the SLM line image are illuminated. And, rather than a singlehorizontal bar as shown in FIG. 15A, a horizontal barcode pattern 1802is used. The horizontal barcode pattern 1802 in FIG. 18A corresponds tothe horizontal barcode patterns 1102 described above with regard to FIG.11.

In FIG. 18A, when the pattern of illuminated pixels 1800 is swept over ahorizontal barcode pattern 1802 having a pattern matching the pattern ofilluminated pixels 1800, the optical correlation signal for a properlychosen pattern yields a single correlation peak. Unlike the examplediscussed with regard to FIGS. 15A and 15B, the single correlation peakis relatively well discriminated from the background.

This single and well-defined correlation peak provides improvedresolution and signal-to-noise ratio relative to the homogeneous blockof illuminated pixels 1502 shown in FIG. 15A.

FIG. 18B illustrates an example including horizontal barcode patterns1804 and a track 1806 including slanted barcode patterns interweavedbetween sets of vertical bars as discussed above with regard to FIG. 17.

The horizontal barcode patterns 1804 in FIG. 18B provide scaling andoffset along the y-axis.

In the case of the slanted barcode patterns, a calibration system (e.g.,1016 in FIG. 10) processes the sampled optical correlation beam for xand y positions, thereby yielding information regarding the scale andoffset for both orthogonal axes in a single scan. This may reducecalibration time while maintaining relatively high accuracy.

FIG. 19 is a graph for illustrating how repeated use of single-scanmeasurements of trajectories may be performed on a calibration plateconfigured as described above with regard to, for example, FIGS. 11 and17 to provide information regarding distortion and deviation over alarger area.

In mask writing, such a calibration plate is commonly referred to as a“golden plate” (GP) and is used to calibrate and/or compensate fordeviations that depend on stage movements.

At least some example embodiments provide pattern generators utilizing acalibration plate or board fixed to a stage. The stage is configured tohold a workpiece to be printed and/or measured.

At least one example embodiment provides a pattern generator including:a writing tool and a calibration system. The writing tool is configuredto generate a pattern on a workpiece arranged on a stage. The writingtool may be an LDI writer, a helix scanner, a rotary scanner, a linearscanner, etc.

The calibration system is configured to determine a correlation betweena coordinate system of the writing tool and a coordinate system of acalibration plate on one of the stage and the workpiece. Whilegenerating the pattern on the workpiece, the pattern generator is alsoconfigured to perform real-time alignment of the pattern based on thedetermined correlation between the coordinate system of writing tool andthe coordinate system of the calibration plate.

As mentioned above, although example embodiments are discussed in someinstances with regard to a rotor or rotating system, example embodimentsare not limited thereto. Rather, example embodiments are applicable todifferent stage concepts and printing technologies such as cylindricalstages, helix concepts for roll-to-roll printing, etc., examples ofwhich are discussed below with regard to FIGS. 20A-35.

Furthermore, example embodiments should not be limited to using adiffracted or reflected portion of an optical writing beam impinging ona pattern of a calibration plate and/or board. Rather, in alternativeembodiments, a separate beam or SLM aerial image impinging on thepattern of a calibration plate and/or board may be used for fastreal-time alignment during patterning.

FIG. 21 illustrates a printing platform including a cylindrical stage.Methods, apparatuses and/or devices described above with regard to theLDI writer shown in FIG. 10 may also be implemented in conjunction withthe printing platform shown in FIG. 21. Because the concepts and/orprinciples of example embodiments are substantially the same as thosediscussed above, a detailed discussion is omitted for the sake ofbrevity.

Referring to FIG. 21, the platform includes a frame 202 having upper andlower supporting structures 213U and 213L and end support structures214L and 214R. The support structures 213U, 213L, 214L and 214R may beformed, for example, of a continuous piece of metallic material (e.g.,sheet metal). As shown in FIG. 21, the support structures 213U, 213L,214L and 214R include a tube 207 formed therein for temperature control.The temperature of the support structures 213U, 213L, 214L and 214R maybe controlled by flowing fluid (e.g., air, liquid, gas, etc.) throughthe tube 207 in direction 217.

Alternatively, the support structures 213U, 213L, 214L and 214R may beformed in a piecemeal fashion, in which each of the support structures213U, 213L, 214L and 214R are formed individually, and subsequentlyassembled.

A cylinder or cylindrical stage 201 is arranged within the frame 202. Inone example, the cylinder 201 may have a diameter of about 1 meter andthe length of about 2 meters.

The cylinder 201 is mounted on a rotating axis 212 using bearings 216. Adriving device such as a motor 203 is attached to one end of therotating axis 212 to drive the rotating axis 212 causing the cylinder201 to rotate in a direction 218. The cylinder 201 may be, for example,about 500 kg and the bearings 216 may be, for example, hydrostatic fluidbearings; however, any suitable bearings may be used. The fluid may be,for example, air, liquid, gas, etc. Hydrostatic fluid bearings arewell-known in the art, and therefore, a detailed discussion will beomitted for the sake of brevity.

In at least one example, a cylinder that is about 1 meter in diameterand about 2.5 meters long may be supported, for example, by hydrostaticbearings. The rotating axis 212 may be an extension of the rotor or maybe fixed.

Referring still to FIG. 21, the temperature of the frame 202 and thecylinder 201 may be controlled by forced cooling. The forced cooling maybe performed by flowing fluid (e.g., liquid, air, gas, etc.) through therotating axis 212 in a direction 206. The temperature of the frame 202and the cylinder 201 may be controlled to a temperature between about 0°and about 0.01° Celsius, inclusive. For example, the cylinder 201 may betemperature controlled to about 0.05° Celsius or to about 0.01° Celsius.

The processing platform shown in FIG. 21 further includes a conveyor 208for transporting workpieces to the cylinder 201. Loading and unloadingof workpieces to and from the cylinder 201 will be discussed in moredetail with respect to FIGS. 25A and 25B.

Referring still to FIG. 21, each end support structure 214L and 214Rincludes a plurality of mounting surfaces 211 upon which a plurality oftoolbars 302 and 310 are arranged, mounted or fixed. Although each ofthe plurality of toolbars 302 and 310 may have a tool mounted thereon,FIG. 21 shows only a single tool 301 mounted on the toolbar 302 for thesake of clarity.

In example operation, the driving device 203 rotates the stage 201 toany angle and the tool 301 slides along the toolbar 302, such that thetool 301 is able to access any point on the surface of a workpieceloaded on the cylinder 201.

The tool 301 may be, for example, a metrology device and/or writing toolfor establishing a more accurate coordinate system on the workpieceand/or for performing fast pattern alignment during patterning. Thecoordinate system may be calculated with corrections for the bending ofthe glass, for example, to provide the true coordinates when theworkpiece (e.g. glass sheet) is later in a flat state.

In one example, the metrology device 301 may include optics (not shown)for reading fiducials on the surface of the glass and/or features of apreviously formed and/or patterned layer on the workpiece. The optics ofthe metrology device 301 may be fixed or slide along the toolbar 302 toaccess any point on the workpiece. The data from the metrology device301 may be used for a variety of operations and/or functions. Forexample, the data from the metrology device 301 may be used for takingmeasurements used in assessing distortion created by high-temperatureprocessing and/or coating/etching. The tool 301 may also be used foraligning analytical, inspection, patterning and/or processing toolsrelative to a formed pattern, creating a distortion map on-the-fly formore accurate overlay between the current operation (e.g., patterning)and the previous pattern, performing fast pattern alignment duringpatterning of a workpiece, and/or monitoring distortion and/or drift inthe coordinate system or support structure.

The platform shown in FIG. 21 has a plurality (e.g., four) of additionalfree positions for toolbars and may hold a plurality of (e.g., five)separate instruments, each one scanning the entire width of the stage.Platforms according to example embodiments of the present invention mayinclude any number of toolbars and multiple tools may be mounted on eachtoolbar.

FIG. 22 shows another example platform. The platform of FIG. 22 issimilar to the platform shown in FIG. 21, except that the platform ofFIG. 22 includes a metrology toolbar 402 and an inspection toolbar 404.The inspection toolbar 404 includes a plurality (e.g., four) of opticalinspection heads 406. The optical inspection heads 406 may be the sameas, or different from, one another.

Referring to FIG. 22, as shown by the arrows the cylinder 201 rotatesand optical heads 404 slide along toolbar 404 to cover the entire widthof a workpiece loaded on the cylinder 201. Each optical head 406 reads astripe of the workpiece with a camera and compares the read stripe to aknown reference pattern. The reference pattern may be a time-delayedportion of the same stripe, a pattern from another tool on the same oranother toolbar or a reference pattern obtained from a database.Comparing the read stripe to a time-delayed portion of the same stripeor a pattern from another tool is referred to as die-to-die inspections,whereas comparing the read stripe to a reference pattern obtained from adatabase is referred to as die-to-database inspection.

The optical inspection heads 406 shown in FIG. 22 may be, for example,cameras, such as time-delay and integration (TDI) cameras.

FIG. 23A illustrates a cylinder arrangement having a plurality of inputsand outputs. FIG. 23B shows an example of how the cylinder may bearranged within a processing track such that the workplaces may becaptured or allowed to pass.

As shown in FIG. 23B, the workpiece 1100 carried on processing track1102 passes over the cylinder 1104 or are taken by the cylinder 1104depending on the desired order of the workpiece 1100 among a pluralityof workpieces, which are not shown for the sake of clarity. For example,if workpiece 1100 need be delayed, then the workpiece 1100 is taken offthe processing track 1102 by the cylinder 1104. While on the cylinder1104, other workpieces may pass-over the cylindrical stage 1104 and beprocessed ahead of workpiece 1100. On the other hand, if no delay isrequired, the workpiece 1100 passes over the cylinder 1104 and continueson the processing track 1102. This arrangement may be used for ananalytical instrument such as those used for sampling quality control.

The cylinder 1104 may also be used to capture, hold, and subsequentlyrelease the workpiece after a period of time to change the order ofworkpieces on the track. As is well-known in the art, changing the orderof two elements in a sequence enables arbitrary sorting, and the abilityto capture and/or hold a workpiece allows sorting of the workpieces.

FIG. 23C illustrates a plurality of cylinders Machine1, Machine2,Machine 3 arranged serially. Although FIG. 23C only illustrates threecylinders, a similar arrangement may include any number of cylinders.

Referring to FIG. 23C, each cylinder in FIG. 23C may be the same orsubstantially the same as the cylinder shown in FIG. 23B, and is capableof passing and capturing a workpiece. Using the arrangement shown inFIG. 23C, the total throughput may be correlated to the number ofcascaded cylinders. For example, the more cylinders, the higher thetotal throughput. Any workpiece may be sent to any of the machines,where the workpiece is processed and then sent back into the materialflow on the processing track. This provides improved flexibility forutilizing the combined capacity of the three pieces of equipment. Thecylinders may also be three different types of equipment, or may be usedfor sorting or changing the order between the workpieces.

Because workpieces may be processed and/or the workflow of theworkpieces changed using a cylinder, more compact processing units suchas the one shown in FIG. 24 may be realized.

FIG. 24 shows an example processing system including a plurality ofcylinders discussed above with regard to FIGS. 23A-23C.

Referring to FIG. 24, workpieces enter from the left (e.g., providedfrom a stocker, which is not shown). The workpieces are coated with aphotoresist and baked at coating station 800. After being coated andbaked, the workpieces are exposed at exposure station 802 and developedat developer 804. After development the resultant resist pattern on theworkpieces are inspected by inspection station 808. If the resistpattern fails inspection, the workpiece is stripped at strip station810, and returned to the coating station 800.

Still referring to FIG. 24, if the resist pattern passes inspection, theworkpiece is etched at etching station 806 and inspected again atinspection station 812. If the workpieces pass inspection or haverepairable defects, the workpieces are output to the stocker or a repairstation accordingly. If the workpiece fails inspection (e.g., theworkpiece is irreparable), the workpieces are output to scrap anddiscarded.

FIG. 25A shows an example horizontal orientation of a cylinder.

FIG. 25B shows an example vertical orientation of a cylinder.

When loading the cylinder horizontally, as in FIG. 25A, a workpiece istaken from a conveyor belt. When loading the cylinder vertically, as inFIG. 25B, the cylinder is loaded from a guide rail system.

When loaded horizontally, the workpiece may be kept in place bygravitational force. In addition to the gravitational force,horizontally loaded cylinders may be held in place by a pusher to forcethe edge of the workpiece down on the cylinder to latch the workpiece inplace. The workpiece may be held in place by a vacuum to ensure that thesurface follows the surface of the cylinder closely.

At the ends of the workpiece the spring force of the workpiece may bethe primary force. Therefore the end of their workpiece is fastened moresecurely to the cylinder. A latch controlled to capture or release theedge of the workpiece may be used. When the edge is released forunloading the pusher takes over the force and follows the end of theworkpiece while being unrolled. The pusher may be contact or noncontacttype.

FIG. 26 shows an example apparatus 2800 for establishing a coordinatesystem on a cylinder.

Referring to FIG. 26, angle encoder discs 2802 rotate with the cylinder2804 and a linear encoder 2806 is arranged along the tool axis. Thetoolbar 2808 references the angle encoder discs 2802 and provides thescale used by the tool. The angle encoders 2802 may suffer from errors,such as, uncertainty in the position of the rotation axis, non-linearityin the angle codes and/or noise.

FIG. 27A illustrates in more detail how a command to move tostandardized workpiece coordinates x and y may be converted to a commandfor the stage and tool to move to specific tool and stage coordinates.Standardized (or abstracted) workpiece coordinates are the coordinateson the workpiece when, for example, the workpiece is in a desired orpredefined state (e.g., unstressed with flat front side at a uniformtemperature of about 22.00° C.). Furthermore the standardized state maybe at a specific time, for example, after the substrate has beenprocessed (with possible distortion, warpage and shrinkage) and will bematched to another panel, for example, a transistor array for a colorfilter. Even though the workpiece may be neither stress-free, flat norin the finished state at the specified temperature, there may still be aone-to-one relation between points on the surface of the workpiece andpoints on the workpiece in the standardized state.

To draw a cross that will appear at a particular x,y coordinate on thefinished, tempered, flat and stress-free workpiece there is, at everypoint in time, a point at which the cross should be drawn. The machinefor drawing the cross may be controlled by tool and stage coordinates.FIG. 27A shows how the stage and tool coordinates for an abstractedcoordinate may be located.

Referring to FIG. 27A, after moving the tool to a standard workpiece x,ycoordinate point at S3600D, the standardized coordinate is corrected fora scale error and for the scale error resulting from the temperaturedifference between the current point in time and the standardized stateat S3602D. At S3604D, systematic distortions, such as shrinkage due tohigh-temperature annealing, are corrected.

At S3606D, clamping and bending distortion are further corrected. Forexample, in this context bending may be dilation of the outer surfacedue to the bending and clamping or other known distortions (e.g.,compression due to holding forces). In at least one example embodiment,it may be relatively difficult to attach the thinner workpiece to thestage with proper (e.g., perfect) alignment. Thus, it may be easier toattach the workpiece to the stage and then measure the mis-alignment tothe stage. In this example, the system may have alignment sensors tomeasure the position of the workpiece in machine coordinates. Themeasured mis-alignment may be applied in the software to the coordinatesystem of the workpiece.

Still referring to FIG. 27A, at S3608D the corrected coordinates arefurther corrected for misalignment to the stage. At this point, theworkpiece coordinates are converted to the coordinates or controlparameters for the stage and the tool at S3610D. In an example with acylindrical stage and angle encoders on the axis, the conversion atS3610D includes converting an angle and a tool distance along the axisof the cylinder to cylindrical coordinates. If the tool has internalcoordinates like a manipulator, a camera or an SLM, these internalcoordinates may also be calculated.

At S3612D, the tool offset is applied to the coordinates. If more thanone tool or more than one toolbar is used, the tool offsets are measuredfor each tool and stored to be used for this correction. In at least oneexample embodiment, the offset of each tool is measured against a commonreference suitable to the nature of the tools. If the tools are camerasor detectors, for example, the common reference may be a commonfiducial. If the tools are exposure tools with light beams, the commonreference may be, for example, a camera, a detector or the like. Forsome types of tools where a reference is not readily at hand or notpractical (e.g., a micro-dispenser), auxiliary alignment systems (e.g.,auxiliary detectors, camera, light sources, etc.) may be used. The tooland stage is then moved according to the converted and corrected stageand tool coordinates at S3614D.

FIG. 27B shows a method for converting tool and stage coordinates intostandard workpiece coordinates. In other words, the method shown in FIG.27B is the reverse of the method shown in FIG. 27A. As shown, forexample, a specific set of stage and tool coordinates are recorded andconverted to abstract workpiece coordinates. Although the methods shownin each of FIGS. 27A and 27B are shown with respect to a particularorder, this is for example purposes only. The sequence between steps ofthe methods shown in these figures may be reversed, one or more stepsmay be skipped and/or two or more steps may be combined into oneoperation.

Referring to FIG. 27B, at S3614E, stage and tool coordinates are input,and tool offset is corrected at S3612E. The tool and stage coordinatesare converted into standard workpiece coordinates at S3610E. At S3608E,the corrected coordinates are further corrected for mis-alignment of thestage.

At S3606E, clamping and bending distortion are further corrected. AtS3604E, any known systematic distortions are corrected. The standardizedcoordinate is corrected for a scale error and for the scale errorresulting from the temperature difference between the current point intime and the standardized state at S3602E. The standard workpiece (x,y)coordinate points are output at S3600E.

FIG. 28 shows a more detailed view of the projection system according toan example embodiment. The drawn stripe may be about 140 mm wide on theworkpiece and the scanning speed along the tool axis may be about 1 m/s.There is an overlap of about 20 mm between stripes. As a result, thethroughput is about 0.1 m²/second or about 6 m² in 60 seconds. Theexposed pattern may be distorted to match a known distortion of apreviously created pattern on the workpiece, or in anticipation of adistortion that may occur or be later in the process due to patterning,stress, high-temperature processing or matching to a distorted element.Intentional distortion along the tool axis may be created using smallchanges in the scanning speed of the mask relative to the speed of theprojection system. In the tangential direction, for example, smalldistortions may be created by a small angle movement of the cylinder, bya mechanical offset or tilt of one of the components in the projectionsystem and/or by a small movement of the mask in a directionperpendicular to the scan direction.

The mask may be flat, but the optical field on the cylinder may becurved. The curved field may be corrected in a ring field system, whichmay be suitable.

FIG. 29 shows several example vacuum or closed environment processes forforming semiconductor and other devices using a cylindrical stage.

Referring to FIG. 29, the cylinder 5101 is enclosed in a hermeticallysealed vessel 5102. The vessel 5102 may be sealed using, for example, avacuum introduced via access point 5105. Alternatively, the access point5105 is used to control the atmosphere of the sealed vessel 5102. Aload-lock 5103 is differentially pumped so that workpieces 5104 areloaded into the chamber while maintaining the vacuum. After the machinehas been loaded, the load-lock 5103 is closed.

Referring still to FIG. 29, within the sealed vessel 5102, thecylindrical stage 5101 is used in a sputtering process 5100A, a plasmaetching process 5100B, inductive plasma etching or deposition 5100C,photon, electron, or ion beam rubbing 5100D and/or laserannealing/re-crystallization 5100E. Each of these processes iswell-known in the art, and thus, a detailed discussion thereof will beomitted for the sake of brevity. In addition, although only processes5100A-5100E are discussed herein, many more processes than those shownmay be implemented using a similar or substantially similar system. Acylinder or cylindrical stage, according at least some exampleembodiments, may also be used as an infrastructure for inspection and/orrepair.

FIGS. 30, 31A-31C, and 32A-32C illustrate different stages usable in amodular system as shown, for example, in FIG. 21.

In more detail, FIG. 30 illustrates a flatbed platform. The platformshown in FIG. 30 may be a lightweight frame, shown for example purposesas a truss. However, example embodiments may be built with thin walledtubes that may be temperature controlled by fluid (e.g., air, waterand/or gas) flowing within the tubes. The frame may provide a more rigidsupport for a stationary stage top 5802 supporting the workpiece 5803.At least one toolbar may extend across the stage multiple toolbars arepossible and standardized seats, fixtures and connectors, plusinfrastructure for the creation of a common coordinate system makes iteasier to configure the stage with one or many tool on one or many toolbars. FIG. 30 shows as an example including four toolbars 5804. Each ofthe toolbars has one or more tools 5805. The tools 5805 are mounted orarranged in a similar or substantially similar manner to that asdescribed above with regard to the cylindrical stage. The number oftoolbars 5804 and the tools 5805 attached to each toolbar 5804 may beconfigured according to the application and/or need for capacity.

FIG. 30 also shows a linear motor 5807 driving the toolbar assembly andthe stator of the linear motor is attached to a rod 5708 connectedbetween two supports 5709, 5710 standing separately on the floor. Inanother example embodiment, a freely moving counter mass (not shown) maybe connected to the stator so that neither part of the linear motor isconnected to the ground. The linear motor moves the toolbar assembly andthe counter mass by applying a force there between, while keeping acommon, stationary center of gravity. A separate system including amotor (not shown) applying a weak force between the ground and thecounter mass keeps the counter mass centered within a range of movement.

FIGS. 20A ad 20B show examples of conventional drum scanners. In thisexample, the workpieces may be a flexible sheet such as plastic film orpaper. In FIG. 20B the substrate is a thin glass sheet intended formaking display devices by thermal transfer, in particular for colourfilter production.

The optical writing units in FIGS. 20A and 20B may be, for example,single point laser diodes. The laser diodes may be of any commercialavailable wavelength such as blue, red, violet, etc. The power of alaser diode may be, for example, about 5 mW to about 65 mW, inclusivefor single mode, and about 5 mW to about 300 mW, inclusive for multimodediodes. An electro-optical efficiency of a laser diode may be, forexample, about 13%. The laser diodes may act as an optical power sourceand a modulator, for example, simultaneously. Alternatively, the opticalwriting units may be SLMs.

The axis of rotation of the rotor scanner may be vertical, horizontal,or any angle there between. The vertical axis arrangement may have aconstant, or substantially constant, acceleration of the optical writingunits at all times. The horizontal axis arrangement may handle theworkpiece more efficiently and/or with less effort absent the need tocounteract forces of gravity.

FIGS. 31A-31C illustrate different implementations and orientations of ahelix writing apparatus including a disc rotor scanner. The disc rotorscanner discussed below with regard to FIGS. 31A-31C may be the same orsubstantially the same as the disc rotor scanner shown, for example, inU.S. patent application Ser. No. 11/711,895. Therefore, a detaileddiscussion will be omitted for the sake of brevity.

Referring to FIG. 31A, the writing apparatus includes a holder (e.g., atubular holder) 710 and a disc rotor scanner 730. The disc rotor scanner730 includes a plurality of optical writing units 740.

The workpiece 720 is arranged inside the workpiece holder 710. A centralaxis of the holder 710 is arranged horizontally in this example. Theholder 710 is kept at a fixed position, while the disc rotor scanner 730rotates and/or moves in a direction parallel or substantially parallelto the central axis. The optical writing units 740 are arranged on anouter edge of the disc rotor scanner 730 in at least one row, but areshown as including two rows in FIG. 31A. The optical writing units 740face an inner surface of the workpiece holder 710.

Referring to FIG. 31B, the central axis of the workpiece holder 710 isarranged vertically. The workpiece 770 is arranged inside the holder 710as discussed above with regard to FIG. 31A. The workpiece 770 is fixedin the holder 710 by forces, which flatten, or substantially flatten theworkpiece 770. Alternatively, the workpiece 770 is fixed to the holder710 by vacuum nozzles. In this example, the workpiece 770 is fixed inthe holder 710 by removing the air between the workpiece 770 and theholder 710. The workpiece 770 and holder 710 is fixed while the discrotor scanner 730 rotates and/or moves vertically (e.g., upward and/ordownward).

Referring to FIG. 31C, the writing apparatus of FIG. 31C is similar orsubstantially similar to the writing apparatus discussed above withregard to FIG. 31B. However, in the writing apparatus of FIG. 31C, theworkpiece 720 and the holder 710 rotate while the disc rotor scanner 730moves in a vertical direction (e.g., upwards and/or downwards).

FIGS. 32A-32C also illustrate helix writing apparatuses.

Referring to FIG. 32A, the writing apparatus includes a holder (e.g., acylindrical stage or tube formed holder) 810, a rotor scanner 830 and aplurality of optical writing units 840. A workpiece 820 is arranged onthe outside of the holder 810. The workpiece 820 is fixed on the holder810 by vacuum nozzles (identified as 850 in FIG. 32B). The rotor scanner830 rotates outside the workpiece holder 810 and optical writing units840 emit radiation in a radial direction inward toward the central axisof the holder 810. The optical writing units 840 may be, for example,single point laser diodes, multi-point laser diodes or spatial lightmodulators (SLMs). The spatial light modulators (SLMs) may be at leastpartially transmissive SLMs capable of creating stamps or patterns 860on the workpiece 820. As shown in FIG. 32A, the central axis of theworkpiece holder 810 may be oriented horizontally.

Still referring to FIG. 32A, in operation the ring rotor scanner 830rotates around the central axis of the holder 810 and moves in an axialdirection relative to the holder 810 and parallel to the central axis ofthe holder 810. In addition, the holder 810 rotates around its centralaxis in a rotational direction opposite to that of the ring rotorscanner 830.

FIG. 32B shows an example including a stationary cylindrical holder 810and a rotating writing head 830. The stationary cylindrical holder 810is capable of holding a wrapped workpiece 820.

Referring to FIG. 32B, the holder 810 includes a slit 870 in which acalibration sensor is arranged. The calibration sensor may be movable orfixed. The writing head 830 includes a plurality of optical writingunits 840 configured to create patterns 860 on the workpiece 820. Analignment camera 880 captures an existing pattern on the workpiece 820such that a written pattern is aligned with higher accuracy, therebyincreasing overlay precision.

FIG. 32C shows an example helix writing apparatus including a rotatingcylindrical holder 810 holding a wrapped workpiece 820 and a stationarywriting head 830. The writing head 830 includes a plurality of opticalwriting units 840 configured to create patterns 860 on the workpiece820. The optical writing units 840 of FIG. 32C may be the same orsubstantially the same as the optical writing units 840 of FIG. 32A.

FIG. 33 is a perspective view of a rotor scanner for patterning a flator substantially flat workpiece.

Referring to FIG. 33, the rotor scanner 1520 includes a plurality ofoptical writing units (not shown) arranged on a flat portion (e.g., atop and/or bottom surface) of the rotor scanner 1520. The plurality ofoptical writing units are arranged such that they emit electromagneticin an axial direction relative to the rotor scanner 1520. In oneexample, the optical writing units may be arranged around the outer edgeof the bottom of the rotor scanner 1520. As shown, the rotor scanner1520 rotates and/or moves along the surface of a workpiece 1510. Thewidth of the rotor scanner 1520 covers the width of the workpiece 1510.In example embodiments, the rotor scanner 1520 scans the workpiece 1510in a varying direction, and forms a relatively shallow run across theworkpiece at an angle such that the arc is not tangent to 0, 45 or 90degrees. This geometry may be used with thicker and/or non-bendablemasks.

FIG. 34 is a perspective view of another writing apparatus.

Referring to FIG. 34, the writing apparatus includes a circular stage1630 capable of holding a workpiece 1610. A writing head 1620 isarranged so as to span at least the diameter of the circular stage 1630.The writing head 1620 includes a plurality of optical writing units (notshown) arranged on a surface portion of the writing head, such thatelectromagnetic radiation emitted by the optical writing heads impingeson the workpiece 1610 during writing.

In example operation, the circular stage 1630, and thus, the workpiece1610 rotate while the writing head 1620 moves perpendicular to therotational axis of the circular stage 1610.

FIG. 35 illustrates another writing apparatus. As shown, the writingapparatus includes a rotor scanner 2200 for generating a pattern on aworkpiece 2202. The example embodiment shown in FIG. 35 is similar orsubstantially similar to the example embodiment shown in, for example,FIGS. 31A, 31B and/or 31C, except that the example embodiment shown inFIG. 35 further includes a workpiece shape controller 2204. Theworkpiece shape controller 2204 scans in the same or substantially thesame direction as the rotor scanner 2200. In at least one exampleembodiment, the workpiece shape controller 2204 scans the workpiece 2202such that the workpiece shape controller 2204 and the rotor scanner 2200stay in constant or substantially constant horizontal alignment.

The foregoing description has been provided for purposes of illustrationand description. It is not intended to be exhaustive. Individualelements or features of a particular example embodiment are generallynot limited to that particular example, but are interchangeable whereapplicable and can be used in a selected embodiment, even if notspecifically shown or described. The same may also be varied in manyways. Such variations are not to be regarded as a departure from exampleembodiments, and all such modifications are intended to be includedwithin the scope of the example embodiments described herein.

What is claimed is:
 1. A pattern generator comprising: a writing toolconfigured to generate a pattern on a workpiece arranged on a stage; anda calibration system configured to determine a correlation between acoordinate system of the writing tool and a coordinate system of acalibration plate on one of the stage and the workpiece; wherein thecalibration system is further configured to determine the correlation atleast partly based on an optical correlation signal, or pattern, in aform of at least one optical beam reflected from at least one reflectivepattern on a surface of the calibration plate; wherein the at least onereflective pattern has areas of differing reflectance, and thecalibration plate is configured to reflect an optical beam forcalibrating the spatial position, focus and dose of the optical beam. 2.The pattern generator of claim 1, wherein the calibration system isconfigured to determine the correlation while the writing tool isgenerating the pattern on the workpiece, and wherein the patterngenerator is configured to perform real-time alignment of the patterngenerated on the workpiece based on the correlation between thecoordinate system of writing tool and the coordinate system of thecalibration plate.
 3. The pattern generator of claim 1, wherein thecorrelation between the coordinate system of the writing tool and thecoordinate system of the calibration plate is determined at least partlyprior to generating the pattern on the workpiece.
 4. The patterngenerator of claim 3, wherein the calibration system is a separatemeasurement system configured to emit, toward the calibration plate, atleast one optical beam arranged in a pattern matching at least onereflective pattern on the calibration plate, and wherein the at leastone optical beam reflected from the at least one reflective pattern onthe calibration plate is further used to determine the correlationbetween the coordinate system of the writing tool and the coordinatesystem of the calibration plate.
 5. The pattern generator of claim 1,wherein the correlation between the coordinate system of the writingtool and the coordinate system of the calibration plate is determined atleast partly during the generating of the pattern on the workpiece. 6.The pattern generator of claim 1, wherein the correlation between thecoordinate system of the writing tool and the coordinate system of thecalibration plate is determined at least partly in between strokes of atleast one writing unit of the writing tool generating the pattern on theworkpiece.
 7. The pattern generator of claim 4, wherein the correlationis determined at least partly in between writing sweeps of one rotorarm.
 8. The pattern generator of claim 4, wherein the correlation isdetermined at least partly in between writing sweeps of two separaterotor arms.
 9. The pattern generator of claim 1, wherein the calibrationsystem is further configured to emit, toward the calibration plate, atleast one optical beam arranged in a pattern matching at least onereflective pattern on the calibration plate, and wherein the at leastone optical beam reflected from the at least one reflective pattern onthe calibration plate is further used by the calibration system todetermine the correlation between the coordinate system of the writingtool and the coordinate system of the calibration plate.
 10. The patterngenerator of claim 1, further comprising: a separate measurement systemconfigured to emit an optical beam arranged in a pattern matching atleast one reflective pattern on the calibration plate, and wherein theat least one optical beam reflected from the at least one reflectivepattern on the calibration plate is used by the calibration system todetermine the correlation between the coordinate system of the writingtool and the coordinate system of the calibration plate.
 11. The patterngenerator of claim 1, wherein while generating the pattern on theworkpiece, the pattern generator is configured to perform real-timealignment of the pattern based on the correlation between the coordinatesystem of writing tool and the coordinate system of the calibrationplate.
 12. The pattern generator of claim 11, wherein the optical beamincludes a line image, and the at least one reflective pattern isconfigured to match the line image of the optical beam.
 13. The patterngenerator of claim 12, wherein the optical beam includes a plurality ofray pencils arranged in a pattern matching the at least one reflectivepattern.
 14. The pattern generator of claim 12, wherein the line imageis an SLM line image.
 15. The pattern generator of claim 12, furthercomprising: at least one optical detector configured to sample thereflected optical beam.
 16. The pattern generator of claim 12, whereinthe at least one reflective pattern and matching line image areconfigured to provide a single peak in a resulting correlation signal.17. The pattern generator of claim 12, wherein the at least onereflective pattern is configured according to a Barker or Barker-likecoding scheme.
 18. The pattern generator of claim 12, wherein theoptical beam includes a set of ray pencils arranged in a one-dimensionalpattern.
 19. The pattern generator of claim 18, wherein the calibrationplate further comprises: a plurality of horizontal reflective patternsmatching the one-dimensional pattern of the optical beam; and aplurality of sets of vertical reflective bars having a set of slantedreflective patterns interlaced between each pair of adjacent set ofvertical reflective bars, each set of slanted reflective patternsincluding a plurality of slanted bars arranged to match theone-dimensional pattern of the optical beam.
 20. The pattern generatorof claim 19, wherein the calibration plate further comprises: aplurality of diffuse pads for calibrating focus sensors by measuring asurface topology of the calibration plate; a chirped raster forcalibration of focus by measuring a modulation of the reflected opticalbeam; a plurality of verification pads for verifying a calibration andverification of timing of pattern exposure; a plurality of linesarranged in a fan-like pattern, for measurement of the angularorientation of the calibration plate; and a plurality of offsetcalibration areas for calibrating a timing offset of the calibrationplate.
 21. The pattern generator of claim 19, wherein the plurality ofslanted reflective patterns and the plurality of sets of verticalreflective bars are interlaced along a trajectory traversed by theoptical beam.
 22. The pattern generator of claim 12, wherein the writingtool is a rotor including at least one rotor arm, the system furthercomprising: a laser source configured to emit the optical beam; arotating prism configured to direct the optical beam to the at least onerotor arm; and a reflector configured to reflect the optical signaltoward the calibration plate.
 23. The pattern generator of claim 1,wherein the stage is a cylindrical stage.
 24. The pattern generator ofclaim 1, wherein the writing tool is a helix writing tool.
 25. Thepattern generator of claim 1, wherein the pattern is generated on theworkpiece by roll-to-roll printing.
 26. The pattern generator of claim1, wherein separate optical beams are used for generating the pattern onthe workpiece and for performing real-time alignment of the pattern onthe workpiece.